1. Technical Field
The present invention relates to improvements in a driving mechanism for causing a traveling unit to reciprocate in an apparatus provided with the traveling unit such as an image reading carriage that reciprocates with a predetermined stroke.
2. Description of the Related Art
Generally, in this type of image reading apparatus i.e. image reading apparatus such as a copier and scanner apparatus, in reading an original document image set on a platen, an optical carriage is mounted with a light source for emitting reading light, and an image reading sensor performs photoelectric conversion on the reflected light from the original document. Therefore, the optical carriage mounted with the light source and reflecting mirrors reciprocates along an image reading area of the platen to scan the original document image.
Therefore, the optical carriage has a frame inappropriate form mounted with a light source lamp and reflecting mirrors, and is configured as a unit, and the unit is supported on guide rails and is configured to be able to reciprocate. Then, thus configured traveling unit reciprocates at a predetermined velocity by a driving motor. As this driving mechanism, driving pulleys are disposed in opposite end portions of the platen, a driving member such as a belt and wire is wound over the pair of pulleys, and the driving member is coupled to the traveling unit supported on the guide rails.
Conventionally, as this driving member, a belt with teeth and wire have been used. Then, in the case of the wire, it is known there are problems such as a kink and position displacement of the winding pulley, and in the case of the belt with teeth, it is known there is a problem in manufacturing accuracy of the belt.
For example, it is proposed in Japanese Patent Application Publication No. H11-286153 that a pair of pulleys with teeth are arranged with an image reading area of the platen therebetween, a timing belt is wound between the pulleys, and on the traveling unit side is provided an engagement member having a concavo-convex surface adapted to the tooth surface of the timing belt.
Further, Japanese Patent Application Publication No. H11-263509 discloses a mechanism as a conveyor mechanism for conveying a sheet etc. in which a timing belt is extended between pulleys, and in fixing a carrier member for transporting a sheet to the belt, the tooth surface of the belt and protrusions on the carrier side are mated with each other and thereby coupled to each other.
As described above, in driving a traveling unit reciprocating with a predetermine stroke, it is widely adopted extending the wire or extending a belt with teeth between a pair of pulleys. However, in the case of the wire, when a position displacement arises in winding by a winding pulley, a winding amount changes and fluctuations in velocity occur in the traveling unit. Concurrently therewith, a kink tends to occur in the wire in winding, and it is known there is a problem in durability.
Meanwhile, when the belt with teeth such as a timing belt is used, it is known there is a problem in dimension accuracy in manufacturing the belt. Generally, the belt with teeth is manufactured by incorporating a core material into a base material such as rubber, and in this forming, the tooth forms are formed. Therefore, when the belt is coupled to the traveling unit simply by screw, through pin or the like, a coupling hole is broken (by the effect of the rubber base material), and it is difficult to fix with reliability and high durability.
Then, as proposed in Japanese Patent Application Publication No. H11-286153 as described previously, it is attempted to mate the tooth surface of the belt with teeth with the tooth surface provided in the fix portion on the traveling unit side. However, it is difficult to prepare the belt length and teeth pitch with precision in manufacturing the belt, and further, to adapt to a span between pulleys of the used traveling unit and a fix position on the traveling unit side, it is necessary to prepare the manufacturing die to adapt to the use conditions.
Therefore, conventionally, this type of driving belt has been manufactured in endless belt form by preparing a manufacturing die adapted to the use conditions. Accordingly, for example, in producing many types of image forming apparatuses in low volume, there is a problem that it is necessary to manufacture driving belts of many specifications. Meanwhile, it is naturally considered that this type of belt with teeth is formed of a belt (open belt) with ends and that the belt end portions are fixed to the traveling unit, but a problem still remains in a method of fixing the belt end portions.
Then, the inventor of the invention attempted to form the driving belt of the traveling unit using a belt (open belt) with ends, and reliably fix the belt end portions in a state with high durability. Then, the inventor arrived at an idea of adjusting the length with respect to the tooth surface of the belt, bending the belt end portions mating with the tooth surface in an orthogonal direction to fix, and thereby enabling the problems such as looseness and breakage (fix portion breakage) to be solved.
It is an object of the invention to provide a traveling unit driving apparatus where a driving belt is manufactured with ease in the case that a traveling unit reciprocates by the driving belt, and concurrently therewith, can be coupled reliably to the unit in a state with high durability.